The Pont du Gard, the Roman aqueduct bridge near Nîmes in southern France, is covered in stones sticking out of its piers and arches. They aren't decoration: they are what's left of how it was built.

• ✓fr.wikipedia "Pont du Gard" (Construction)
• ✓en.wikipedia "Pont du Gard"
• ✓Structurae, Pont du Gard
• ✓Pont du Gard press kit 2023 (pontdugard.fr)
• ✓Fiches 2001; Fabre, Fiches & Paillet 1991 (via Wikipedia)
• ✓UNESCO WHC 344

These stones stick out all over the Pont du Gard in France. They look like decoration. They're not. It's a Roman aqueduct, a hundred and sixty feet tall, built to carry water to Nîmes. Its great arches have no mortar: blocks of up to six tons just sit on each other. Look closer. Right where each arch starts to curve, there's a ledge. It held a temporary wooden arch used to lay the stones. The stones sticking out everywhere else held up the builders' scaffolding. When the work was done, the builders could have chiseled all of this off. They didn't. So this bridge isn't decorated. It's still wearing its construction kit, two thousand years later. Subscribe for a fact every day.